[HDDS-4143] Implement a factory for OM Requests that returns an instance based on layout version.

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.1.0
• Component/s: Ozone Manager
• Labels: pull-request-available
• Target Version/s: 1.2.0
• Assignee: Aravindan Vijayan
• Reporter: Aravindan Vijayan
• Created: 24/Aug/20 18:44
• Updated: 25/Jan/21 17:14
• Resolved: 15/Sep/20 17:41

Description

• Add the current layout version (MLV) to the OM Ratis request. If there is no layout version present, we can default to '0'.
• Implement Generic factory which stores different instances of Type 'T' sharded by a key & version. A single key can be associated with different versions of 'T'. This is to support a typical use case during upgrade to have multiple versions of a class / method / object and chose them based on current layout version at runtime. Before finalizing, an older version is typically needed, and after finalize, a newer version is needed.
• Using the generic factory, we scan all the different OM "write" requests and associate them with versions.
• Layout feature code refactoring. Added more comments and tests.

Issue Links

• links to: GitHub Pull Request #1405